1. Field of the Invention
This invention is in the general field of doors for buildings, and is most particularly directed to doors which open upwardly in warehouses and the like, and even more particularly directed to such doors wherein a barrier is provided to prevent vehicles or persons passing through the door when not fully opened, and is even more particularly directed to such a barrier for a door as described wherein the barrier is automatically removed when the door open condition reaches a predetermined attitude.
2. Description of the Prior Art
I know of no prior art providing for a barrier to prevent passage through a partially opened door, which barrier is automatically removed when the door is fully opened, or when other predetermined conditions with relation to the door are achieved.